Improvement of flexural capacity of hybrid, reinforced concrete spliced girders using steel fiber concrete in splice region and near surface mounted carbon fiber‑reinforced polymer bars: experimental investigations

摘要

Large span girders (more than 50 m) are difficult to cast as one unit for several conditions, it is better to assemblage them from precast segments in field. This paper aims to investigate the structural behavior of simply supported reinforced concrete spliced girders. Seven beams with 150 x 250 mm rectangular cross section and 2200 mm total length have been cast. The first beam was cast as one unit as a control beam while the other six beams were made from two precast segments spliced at midspan using cast in situ joints. The parameters studied were the existence of splices, joint length, use of steel fiber concrete at joint region, and strengthening the spliced girders using near surface mounted carbon fiber-reinforced polymer NSM-CFRP bars. All beams were tested using four points loading system. The results showed that the existence of splices decreased the flexural capacity of the spliced beam by about 24.1% with larger midspan deflections if compared with the control beam. Also, decrease in joint length by 50% decreased the flexural capacity by 20.1%, 24.1%, and 25.7%. When steel fiber concrete of 1% volume fraction was used at joints, the flexural capacity of the beams increased by 23.4-32.7%. In addition to that, providing the spliced beams with NSM-CFRP bars of amount 50% of the main tension steel reinforcement enhanced the load carrying capacity by 38.5-83.7%. In spite of that, the failure of the beams was rather brittle.